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H. J. DE N. MCCOLLUM HEATER Filed Nov. 4, 1942 July 31, 1945.

H. J. DE N. MccoLLUM 2,380,602

" HEATER Filed Nov. 4, 1942 2 Sheets-Sheet 2 Patented July 3i, 1945 estatut MAIER Henry J. De N. McCollum, Chicago, Ill.; Thea McCollum McCollum, deceased executrix of said Henry J. De N. A

Application November 4, 1942, Serial No. 484,451

` a claims. (omas-11s) The present invention relates to heaters particularly of the internal combustion type. and

more especially heaters of this type adapted for use in aircraft. 4

It is one ofthe objects of the present invention to provide a novel heater of the above type which is eillcient and safe in operation and which has a maximum of' heat output, together with a minimum of weight.

Yet another object of the present invention is to provide an internalcombustion heater oi the above type having an improved arrangement for quieting and steadying the operation of the heater and preventing pulsations known as ',mo-`

tor boating."

casing ill moves past a plurality of heat ex- I change fins. indicated generally by the numeral Still another object of the present invention is to provide a novel heater having any,or all of the above advantages which can be manufactured in production at comparatively low' cost. Yet another object of the present yinvention is to provide a novel internal combustion heater having 'improved heat exchange mechanism.

Other objects and advantages will become apparent from theV following description of a preferred embodiment of my *invention illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer to similar parts throughout the several views, v f

Fig. 1 is a vertical longitudinal sectional view x through the major portion of a heaterembodying the present invention;

Fig. 2 is an end view of the heater illustrated in Fig. 1 is seen from the right;

, Fig. 3 is an end view of the heater illustrated: in Fig. 1 as seen from the left;

Fig. 4 is a transverse sectional view of a fraction of the heater drawn to larger scale. It may be considered as taken in the direction of the arrows substantially along the lines Il-I' of Fig. l; andl Fig. 5 la a longitudinal sectional view` oi a fraction of the? heater mechanism drawn to largerscale. This view may be considered. as

taken in the direction of the arrowsalolng the The heater illustrated `in 1 of the draw;

ings is intended to receive air for its operation from oneor more air rams. theserams being located at the leading edge of the airplane wing' or in some other -position where they face.

against the moving air stream. Air from the ram or rams passes into the inlet end of a tubular casing I0 and into the inlet end of a fuel -induction tube i2. The air passing into the il. and out of the opposite end le of the casing to the space to be heated..

Air entering the induction tube l flows through a Venturi throat le into a combustion chamber 20 around an acoustic silencer 222 to an exhaust collecting space 2d. From the collecting space 24 the gases are passed Voutwardly through a fitting 28 to a position outside oi the airplane or to some other low'lpressurearea..

This fitting includes a venturi type restriction 2B which serves to smooth out irregularities in the pressure differential at the two ends of the heater.-

The air intake vent' tu, is located within the 'I air induction tube i2 and faces against the direction of air iiow therethrough. A set of fuel asprating lets 32 are locatedwithin the Venturi throat I8; These Jets'. therefore, are'at a lower pressure than the air within the intake vent 30. This pressure differential 'is used in any well'known manner to cause a ow of liquid fuel from a carbureting device, indicated by the numeral 34, to the Jets 32. The carbureting device 34 isv not illustrated in detaill inasmuch as the construction of such devices is well,- known and need not be described in detail here in- 'order to illustrate the present invention.

The combustible mixture formed at the Venturi throat i8 passes forwardly and thence radially outwardly through a plurality of ports t@ formed by striking vanes outwardly/'from the side wall of va cylindrical tube 38, which ex tends a short distance into the .combustion chamber- 20. The vanesY are bent outwardly in an oblique manner and .therefore cause the combustible mixture toventer the combustible chamber with a swirling motion. This produces considerable turbulence within the coin-y ,bustion chamber and'aids in the maintenance of` uniform, eflicient combustion.,

Within the combustion chamber one or more igniters 40. three being shown in the Present embodiment, raise the temperature of acomparatively isolatedportion of lthe combustible mixture to the ignition point and thus bring about a burning within the combustion chamber. 'I'he not products of combustion thus formed pass rearwardly and out through the fitting 26.

The igniters 40 shown are of the hot wire type and are described in detail in my co-pending ap' plication, entitled Heating apparatus," Serial No. 441,345, nled June 17, 1942.4 These igniters are energized until the heater has been. placed in operation. The heat produce by the burning combustible mixture actuates a t ermostatic element. not shown, in a well known manner and n causes deenergization of the igniters 40.

. v22 and through longitudinally extending passages l 6d formed in the side walls oi the heat exchange member i4 constructed in a manner to be described presently. The side walls of the passages absorb the heat from the hot gases and this heat is transferred to the air stream passing through the casing I in an annular stream around the combustion chamber.

As best illustrated in Fig. 4, the wall vof the heat exchanger is formed of a length of longitudinally corrugated tubing, indicated generally by the numeral 68. The'creases in the tubing wall whichform the corrugations are substan.

tially rectangular. thus dividing the wall of the tubing into a plurality of inner and outer longitudinally extending substantially rectangular slots, The inner surface of this tubing rests against the outer circumference of the rearward portion of the acoustic silencer 22, thus forcing the hot gases to -iiow through the inner passages 44 in intimate heat transfer relation to the tubing wall. y l i The acoustic silencer 22 is formed of a rearward generally'cylindrical portion 48 fitted to the interior surface of the heat exchange tube 68. Just ahead o! the cylindrical portion mentioned, the side wall of the silencer converges inwardly slightly, as indicated at B U, while ahead oi this portion,the wall of the silencer slopes inwardly still more abruptly. as indicated` at 52,' the extreme forward end o t the silencer being closed by a conical nose can 54. i This arrangement provides good turbulence within the combustion chamber while at the same time moving the hot products of combustion outwardly into the longitudinally extending passages without the formation of hot spots within the combustion chamber, which are likely to cause deterioration oi' the heater and produce other disadvantageous effects.

A pair oi concentric inner and outer tubes 56 and 58, respectively, are arranged within the portions 48 and 80 and are secured to a disc 80 which closes the rearward end oi the acoustic silencer. The concentric tubes 58 and. B8 and the side wall portions o8 and 5B are perforated,l the holes forming these periorations in the'present instance being approximately a sixteenth oi an inch,-

in diameter and arranged on quarter inch centers.

a,sso,oos

resistance to damp out pulsations. Further, these holes are oi such size that ilame cannot be propagated -through into the' interior of the silencer. 'I'his is important because s. quantity oi combustible mixture may collect within the in- ;lerlor oi' the silencer during operation ea er.

by providing the corrugated tubing 48, previously mentioned, cut to appropriate length. This tubing may be formed by corrugating a sheet, and then forming the sheet into a tube with overlapping edges crimped together. As best shown' in Fig. 5, each end of this tubing is seated in an annular groove in the face 84 oi' an end ring IE. Two thin metal fin strips G8 are then placed face to face and inserted in one oi the outer slots formed by the corrugations in the tube 46. These iin strips extend longitudinally substantially the full disitance between the two rings 66, and extend outwardly almost the distance between the corrugated tube and the casing i6. Other pairs of n strips are similarly inserted in the other outer slots in the side wall of the corrugated tubing d6 until all oi these slots are filled; Preferably the iin strips are formed with spaced slots extending inwardly from their outer edges to approximately the outer surface of the corru gated tube. These slots separate the fin strips into a pluralityof tabs It and thus prevent warping of the fins as might otherwise take place with successive heating and cooling. The assembled heat exchange structure is then placed in an oven and braced to forxnthe several elements the corrugated tube 8B into a plurality of lon- Between the wail portions I8 and 60 and the tube 5&3, and between the tube B8 and the tube at, a plurality oi annular plates B2 divide the spaces between the several general cylindrical members into a plurality ofi annular chambers. The inner row ci plates is staggered with relation .to .the outer row so that gases passinginwardly through the pericrations will meet with auiilcient into an integral unit. When a heater of this type is intended to be used in an airplane. it is preferable that the corrugated tube and the fins. a8 welly v as the rings 88,'be formed of aluminum. Under these. conditions, I prefer tov use a brazing'fiux comprised of to 95% aluminum, and 10 to 5% silicon. Or, if desired, aluminum sheet, commonly-known as 2S. or 3S aluminum can be obtained already coated with a layer of 90 to 95% aluminum and litto 5% siliconI in which case no flux is necessary. In some instances, the corrugated tube and iins may preferably be formed of copper or a copper alloy, in which case the elements can bev brazed in the ordinary copper brazing manner.

. Each of the two iin strips. comprising one pain-is bent outwardly away from each other asbest shown in Fig. 4 so. that the outer' edge of each of the tln strips is comparatively close to the outer ecigeof the contiguous n strip in the next adjacent slot. This arrangement divides the air space between the casing I0 and gitudinally extending triangular passages 'I2 oi approximately equal volume. Thus. the amount 1 of air flowing on one side of any one ot the iin, strips will be approximately the same as the amount oi air on its opposite side. This, in effect, meansthat-the temperatures of the air on each side ot each o1 thel iln strips will be approximately` equal, thereby producing good heat v exchange eiilciency.

The forward ring 68 is secured to a circular plate 'lo by a plurality o! nuts 'it threaded to studs lil.' threaded at their opposite ends into the ring S8. The plate 'i6 acts as ae'iosure for 'the forward end oi the combustion chamber o! the The heat exchange portion i4 is constructed.

. is secured' to 'a strap metal spider 80 by clamping or by brazing, the spider having legs extending outwardly where they are, secured to the casing I0 by. screws 82, thus centering the combustion chamber and heat exchanger relative to the casing I0.

The plate 14 is also provided with one or more, in the present instance three, threaded fittings 84 which receive the igniters 40. These igniters are energized through a branched cable 88 which passes to a connector block 88 secured in the side wall of the casing I0.

At the opposite end of the heat exchanger, the ring 86 is similarly secured to an annular plate 90 having a comparatively large opening therethrough. This plate is brazed or otherwise suitably secured to a sheet metal cap 82 which forms the closure for the outlet end of the burned gas passage, and which is shaped to deiiect the exhaust gases to` one side where these gases pass through the outlet fitting 28, this outlet. tting being threaded into a ring 84 brazed to the sheet metal cap 92.

The outlet end of the heat exchanger is aligned within the casing l by means of 4a. leg 98, brazed to the cap 82 at one end and secured to the sheet metal casing I0 by means of a screw 98 at its opposite end. Additional support is provided'by means of a transversely extending bracket Illl), secured at its opposite ends to the casing i0 by means Aof screws |02 and which, at its central portion, is clamped to the ring 88 into which the outlet fitting 28 is threaded.

The acoustic silencer is dimensioned so as to have a slip t within the corrugated tube 48 and is properly located in a longitudinal direction therein by means of a threaded rod |04, this rod being brazed at one end to the plate 80, while its opposite end extends through an opening in the sheet metal cap 92. The end whichjprojects through the sheet metal cap is threaded to receive a nut |08 which, when tightened, clamps the adjacent portion of the sheet metal cap against an upset head |08 formed upon the rod |04 in a position just inside the cap.

When a heater of the above type is intended for use in an aircraft, I prefer vthat the acoustic silencer be builtup of comparatively thin stainless steel parts spot or seam welded together, excepting that the nose cap 54, which is at the highest temperaturev point, be made from "Inconel or similar heat and corrosion resistant material. The re-igniter 42 also preferably is constructed of sheet Inconel or similar ma brazed together vin the manner previously de-' scribed.

rugated tube 48. The heat will be absorbed by this corrugated tubing and will be transferred to the nn strips 88 which project outwardly into theannular space between the corrugated tubing and the casing I0. Air flowing through the casing I0 will be forced outwardly by the com- Y bustion chamber portion of the heater so as to flow through the longitudinally extending substantially triangular .passages I2 arranged between adjacent fin strips 88. The fresh air thus efficiently absorbs the heat produced within the combustion chamber 20. At. the opposite end of the heat exchanger, the comparatively cool products of combustion are collected and passed outwardly through the fitting 28,' while the heated air passes from theoutlet end of the casing I0 to the space to be heated.

By constructiong a heater in the manner shown, high heat output can be obtained froma heater of extremely low weight and small size. It will be apparent also that such'a heater fulfills the other objectives set forth for the invention at an earlier portion of this speciflcation.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that numerous modifications and variations may be made without departing from the underlying principles of the invention. I therefore desire, by the following claims, to include within the scope of the invention all such modifications and variations by which substantially the results thereof may be the same or equivalent 40 forming a combustion chamber and longitudinally During the operation of the heater, combusextending heat exchange passages connected to said combustion chamber, means for conveying air to be heated longitudinally and externally of said tube, said silencer comprising a generally cylindrical .portion` and a portion for deflecting products of combustion outwardly into said heat exchange passages, said silencer having a perforated side wallover at least a portion of the area thereof, and means -within said silencer forming perforated sound damping chambers communicating with the first said perforations.

2. A heater comprising a generally tubular element having grooves formed' in the side wallv thereof, means to produce a uid flow through said tubular element, means located within said tubular element to form with said tubular element and said closures a combustion chamber and uid passages connected to said combustion chamber, the last said means comprising an acoustic silencerl having a generally cylindrical portion and a tapering nose to deflect iluid from said combustion chamber outwardly into said passages, said acoustic silencer being perforated over at least its generally cylindrical portion, means within said silencer forming a group of perforated sound damping chambers communicating with said perforations, and means forming a second set of perforated sound damping chambers communicating with the rst set of sound damping chambers.

3. A y heater comprising a generally tubular element having grooves formed in the side wall thereof, means to produce a fluid -ow through said tubular element, means located within said 4 I ,ssacos tubular element to iormvwith said tubular element and said closures a combustion chamber and uid passages connected to said combustion chamber, the last said means l`comprising an acoustic silencer having a generally cylindrical portion anda tapering nose to denect iluid from said combustion chamber outwardly intcsaid pas- 

